A device may execute multiple applications simultaneously. For example, a device may be executing e-mail applications, web browsers, and games, as well as any application that generates viewable content. For each application, the device may generate a graphical window for presentation to a user of the device. Each window may be a two-dimensional box, and the visual content generated by each application may be present within the boundary of each respective graphical window. For example, visual content from an e-mail application may be displayed in the graphical window for the e-mail application. Visual content from a web browser application may be displayed in the graphical window for the web browser application, and so forth.